One of the most hilariously accurate depictions of the "girl world" also happens to be an awesome source of inspiration for easy Halloween costumes. Mean Girls will probably go down in history as the most fetch female movie known to womankind, so why not throw together the groolest getup based on your favorite character from the movie? We've got some ideas that hit the nail on the head — from Karen's sexy mouse to Cady's "ex-wife" costume that terrified quite a few innocent partygoers. Here are 29 ideas that will help you get in touch with the mean girl inside of you.